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Fixed #29908 -- Fixed setting of foreign key after related set access if ForeignKey uses to_field.

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Adjusted known related objects handling of target fields which relies on
from and to_fields and has the side effect of fixing a bug bug causing
N+1 queries when using reverse foreign objects.

Thanks Carsten Fuchs for the report.
This commit is contained in:
Simon Charette 2018-11-01 01:10:29 -04:00 • committed by Tim Graham
parent 413583e2e2
commit 75dfa92a05
5 changed files with 49 additions and 23 deletions
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35
django/db/models/query.py
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@ -61,6 +61,16 @@ class ModelIterable(BaseIterable):
init_list = [f[0].target.attname
for f in select[model_fields_start:model_fields_end]]
related_populators = get_related_populators(klass_info, select, db)
known_related_objects = [
(field, related_objs, [
operator.attrgetter(
field.attname
if from_field == 'self' else
queryset.model._meta.get_field(from_field).attname
)
for from_field in field.from_fields
]) for field, related_objs in queryset._known_related_objects.items()
]
for row in compiler.results_iter(results):
obj = model_cls.from_db(db, init_list, row[model_fields_start:model_fields_end])
for rel_populator in related_populators:
@ -69,19 +79,18 @@ class ModelIterable(BaseIterable):
for attr_name, col_pos in annotation_col_map.items():
setattr(obj, attr_name, row[col_pos])
# Add the known related objects to the model, if there are any
if queryset._known_related_objects:
for field, rel_objs in queryset._known_related_objects.items():
# Avoid overwriting objects loaded e.g. by select_related
if field.is_cached(obj):
continue
pk = getattr(obj, field.get_attname())
try:
rel_obj = rel_objs[pk]
except KeyError:
pass # may happen in qs1 | qs2 scenarios
else:
setattr(obj, field.name, rel_obj)
# Add the known related objects to the model.
for field, rel_objs, rel_getters in known_related_objects:
# Avoid overwriting objects loaded by, e.g., select_related().
if field.is_cached(obj):
continue
rel_obj_id = tuple([rel_getter(obj) for rel_getter in rel_getters])
try:
rel_obj = rel_objs[rel_obj_id]
except KeyError:
pass # May happen in qs1 | qs2 scenarios.
else:
setattr(obj, field.name, rel_obj)
yield obj